1. Field of the Invention
The present invention relates to an active matrix driving apparatus and an active matrix driving method used for, for example, an active matrix liquid crystal display device including a ferroelectric layer having a memory function, instead of a switching device.
2. Description of the Related Art
According to a known active matrix driving apparatus, an electric field is applied to a liquid crystal and the like, utilizing a memory function of a ferroelectric layer which is realized by spontaneous polarization thereof. In such an active matrix driving apparatus, before a data pulse corresponding to display data is applied to the ferroelectric layer, a reset pulse having an opposite polarity to the data pulse should be applied to the ferroelectric layer in order to cause spontaneous polarization in the ferroelectric layer in an opposite polarity to that of the display data.
FIG. 13 shows a liquid crystal display device (hereinafter, referred to as the "LCD device") having data signal lines X.sub.1, X.sub.2, X.sub.3, . . . and scanning signal lines Y.sub.1, Y.sub.2, Y.sub.3, . . . in a lattice. FIG. 14 shows a conventional manner in which such an LCD device is AC-driven by way of field-by-field inversion. In a first field, a reset pulse R having a potential of -V is applied to all the scanning signal lines Y, and then a data writing pulse W having a potential of +V is sequentially applied to each of the scanning signal lines Y. In a second field, by inversion, a reset pulse R of +V is applied to all the scanning signal lines Y, and then a data writing pulse W of -V is sequentially applied to each of the scanning signal lines Y. To a data signal line X.sub.1, for example, a reset pulse R of .+-.V having an opposite polarity to that of the reset pulse R applied to the scanning signal lines Y is applied. Then, to the data signal line X.sub.1, a data pulse D of .+-.V having an opposite polarity to the data writing pulse W is applied when a display state is ON, and a data pulse D having a potential of 0 V is applied when the display state is OFF. As a consequence, for example, an area of a ferroelectric layer corresponding to a pixel at (X.sub.1, Y.sub.2) in FIG. 13 is first supplied with a reset pulse R of .+-.2 V and then with a data pulse D of .+-.V having an opposite polarity to that of the reset pulse R applied thereto or a data pulse D having a potential of 0 V in each field. When a data writing pulse W is applied to the scanning signal line Y.sub.2, the above area of the ferroelectric layer is supplied with a data pulse D of .+-.V or .+-.2 V in correspondence with the data pulse D applied to the data signal line X.sub.1. When the above area of the ferroelectric layer is supplied with a data pulse D of .+-.2 V having an opposite polarity to the reset pulse R applied thereto, data for the display state of ON is stored in the ferroelectric layer corresponding to the pixel at (X.sub.1, Y.sub.2).
In the above-mentioned active matrix driving apparatus and method, since a reset pulse R is first applied in each field, a display screen first goes into a state of displaying nothing, and then pixels of the display screen are sequentially enabled to display data in the order of being scanned by the scanning signal lines Y. As a result, the pixels on the scanning signal lines Y.sub.1 are enabled to display data immediately after the display screen goes into the state of displaying nothing, but the pixels on the scanning signal lines Y.sub.2 and Y.sub.3 are enabled to display data with a delay. The pixels on the other scanning signal lines are enabled to display data with a further delay, and thus are enabled to display data for quite a short period until the next field.
For the above-mentioned reason, an LCD device driven by a conventional active matrix driving apparatus and method utilizing a memory function of a ferroelectric layer has problems in that there occurs a large difference in display contrast between a pixel scanned first and a pixel scanned much later. Such a difference significantly lowers the display quality in a still picture as well as in a moving picture. The uses of the LCD device is quite restricted by these problems.